Light can be represented as electromagnetic fields which vary sinusoidally and orthogonal to the direction of propagation as shown in FIG. 1. [where the direction of propagation is along the Z-axis.] In FIG. 1 the electric field component of the wave is denoted by E, and the magnetic field component is denoted by B.
For the purposes of this invention it is only the electric field component of the wave which will interact with matter and produce relevant phenomena. An electric field is simply the force per unit electric charge in a region of space. Equivalently, if an electric charge were in a region of space occupied by an electric field it would experience a force equal to the electric field times the magnitude of the charge.
Electric fields can be represented mathematically as vector quantities indicating their magnitude and direction at a specific point or in a given region of space. FIG. 1A is the electromagnetic wave in FIG. 1, but with the view looking down the axis of propagation, the Z-axis. FIG. 1-A shows some possible orientations of the electric field. These are only some possibilities. Any orientation in the plane normal to the direction of propagation is possible. That plane is represented as the plane that the circle in FIG. 1A occupies.
As light, an electromagnetic wave, propagates, the behavior of the electric field in space and time is determined by Maxwell""s equations, which are a set of equations defined by James Clerk Maxwell which constitute the physical laws of electromagnetism. Maxwell""s equations have solutions for traveling waves where the electric field varies along an axis as in FIG. 1, varies in a circular of elliptical manner, or varies randomly.
The orientation of the electric field vector and how it changes with time is known as the state of polarization of the electromagnetic wave or just simply the polarization of the light. If the electric field is confined to a single axis as in FIG. 1 it is said to be linearly polarized. In FIG. 1 it is linearly polarized in the X or vertical direction. Since the electric field at any given moment is confined to a plane parallel to the direction of propagation and a plane is two dimensional, there are only two possible independent polarization states for light. We can think of them as horizontal and vertical. Although in physics and mathematics the two unique polarization states used are sometimes right and left circular polarization, these states are simply combinations of vertical and horizontal states that vary in time in the right way to represent an electric field that rotates in a circular clockwise manner or counterclockwise as the wave propagates.
If the electric field in FIG. 1 is not confined to a single axis in the plane but has an equal probability of being in the horizontal or vertical direction and there is no specific time relationship between the vertical and horizontal electric fields the light is said to be unpolarized or randomly polarized.
The electric field can be polarized and confined to an axis that makes an angle, xcex8, with the horizontal or x-axis as shown in FIG. 1B. Since the electric field is a vector quantity when it is polarized in this manner, it can be broken up into horizontal and vertical components. In figure 1B the horizontal axis is the x-axis and the vertical axis is the y-axis. The electric field E in figure 1B has a horizontal component equal to E cos xcex8 and a vertical component equal to E sin xcex8, this being a trigonometric fact. It can be said that the electric field in FIG. 1B has a part of itself, E cos xcex8, polarized along the x-axis and the rest of itself E is sin xcex8, polarized along the y-axis. The sides of the triangle in FIG. 1B formed by E, E cos xcex8, and E sin xcex8 obey the Pythagorean theorem, which means they obey the relations E2 cos2xcex8+E2sin2 xcex8=E2. For the purposes of our discussion it must be understood that the electric field E has a component E cos xcex8 polarized in the x-direction and a component E sin xcex8 polarized in the y-direction.
Some materials act as polarizers. If randomly polarized light enters into a slab of finite thickness of polarizing material with the material""s polarization oriented say in the vertical direction, the horizontally polarized portion of the incident light is absorbed and the vertically polarized portion is allowed to pass through the material. The result is that the light emanating out of the polarizing material is polarized in the vertical direction thus polarizing materials polarize light.
One can think of polarizers as having a transmission axis or sense and an absorption axis or sense. It is more general to use the word sense than axis since axis implies the idea of linearity to the imagination of the reader and that does not apply to circular polarizers and so can become confusing when one is trying to provide broad and general clarity.
If linearly polarized light oriented in the vertical direction enters a linear polarizer whose absorption sense is oriented in the vertical direction the light will be absorbed. Equivalently, if linearly polarized light enters a polarizer whose absorption sense is equal to the polarization sense of the light, the light is absorbed. If linearly polarized light enters a polarizer whose absorption sense is orthogonal to the polarization sense of the light the light is transmitted.
The same statements of what happens physically can be made using reference to the transmission sense of the polarizer. For instance, if linearly polarized light enters a polarizer whose transmission sense is equal to the polarization sense of the light, the light is transmitted. If linearly polarized light enters a polarizer whose transmission sense is orthogonal to the polarization sense of the light, the light is absorbed.
Circular polarizers have an absorption sense and a transmission sense as well. The above reasoning carries through for circular polarizers and circularly polarized light. For instance if circularly polarized light enters a circular polarizer with an absorption sense equal to the polarization sense of the light, the light is absorbed. If the absorption sense of a circular polarizer is left, left circularly polarized light is absorbed when it enters the polarizer, etc.
To expand our vocabulary to encompass an understanding of the relationship between linear polarization (of light or materials), circular polarization (of light or materials), and light that is unpolarized the following facts must be rigorously observed.
(1) Unpolarized light can be represented as an equal mixture of horizontal linearly polarized light and vertical linearly polarized light, where the time relationship between the vertical and horizontal linearly polarized states is random.
(2) Unpolarized light can also be represented as an equal mixture of right circularly polarized light and left circularly polarized light, where the time relationship between the right and left circularly polarized states is random.
(3) Linearly (horizontal or vertical) polarized light can be represented as a linear combination of right and left circularly polarized light, where the time relationships between the right and left circularly polarized states is specific.
(4) Circularly (right or left) polarized light can be represented as a linear combination of horizontal and vertical linearly polarized light, where the time relationship between the horizontal and vertical linearly polarized states is specific.
The above facts can be derived from Maxwell""s equations or from the quantum mechanical theory of light. Both methods produce the same results. Further the above facts have been verified by experiment with great rigor.
If circularly polarized light enters a linear polarizer the part of the light that has a polarization sense equal to the transmission sense of the polarizer is transmitted and the other part has a polarization sense equal to the absorption sense of the polarizer and is absorbed. The same holds for linearly polarized light that enters a circular polarizer.
Some linear polarizers are composed of metal crystals aligned along a specific direction. These are also called metal polarizers. Metal polarizers do not have an absorption sense but have instead a reflection sense. The orthogonal sense to their reflection sense is their transmission sense. Metal polarizers relate to some aspects of this invention.
The making of sheet polarizers, polarizing material on large sheets of substrates, was pioneered by Edwin H. Land and more by John F. Dreyer. The polarizing layer on these substrates is called a dichroic layer. The phenomena of polarizers and polarizing sheets relate to this invention.
Other materials are largely transmissive, meaning their reflecting qualities are minimal. That is to say when one shines light on them the majority of it goes through them without being reflected or absorbed. Transparent and transmissive materials relate to this invention.
Other materials are partially transparent and diffusive. Diffusive means that they scatter light in many directions. Intrinsically, this diffusive quality is due to natural perturbations in the index of refraction. Extrinsically the diffusive quality is due to pores, grain boundary defects, strain fields, small quantities of particulate matter, and crystallographic defects. Optical materials are generally made to minimize the diffusive quality but in some designs of the proposed invention it is desirable to have a partial diffusiveness. Candidate materials that have a partial diffusiveness include; alkali and alkaline earth halides such as chlorides, bromides, iodes, BaF2, PbF2; oxides such as A12O3; oxynitrides such as ALON; chalcogenides such as ZnSe and ZnS; and semiconductors such as Si, Ge, and Go, As. The extrinsic diffusiveness can be adjusted depending on how the materials are made. For more details see, Optical Materials, Ed Solomon Musikant; Marcel Dekker, Inc., 270 Madison, N.Y., N.Y. 10016. The partial transparency is a achieved by using only a thin layer of such materials.
Polarizing layers and diffusive layers can be combined as parallel elements onto substrates to produce laminates that can be used for various purposes. Various prior art techniques have been developed to produce such combinations of parallel elements for various purposes. See U.S. Pat. No. 2,776, 598 to Dreyer, U.S. Pat. Nos. 2,788,707 and 2,9997,390 to Land, U.S. Pat. No. 4,025,688 to Nagy et al., U.S. Pat. No. 5,347,644 to Sedlmayr et al.
When polarizers are spoken of, it shall be understood to mean either a circular or linear polarizer.
If light is traveling through air and enters a material it bends or is scattered. How it is scattered is dependent on the property of the material known as the index of refraction. The index of refraction is commonly denoted by the parameter n, in the literature. If light of wavelength, xcex, is traveling in air and enters a second medium with an index of refraction, n, the wavelength of the light is decreased to xcex/n.
The refractive index is often written as a complex number. The real part has the dielectric constant in it and the imaginary part contains the conductivity.
A weakly conducting dielectric sphere means the material is essentially an insulator.
When refractive index, n, is spoken of it shall mean, n={square root over (xcex5xcexc/xcex50xcexc0)}. Where: xcex5 is the electric permittivity of the material, xcex50 is the electric permittivity of free space, xcexc is the magnetic permeability of the material, and xcex50 is the magnetic permeability of free space. For most materials xcexc≈xcexc0 and n≈{square root over (xcex5/xcex50)}. This is the square root of the dielectric constant. n, is a function of the wavelength (thus frequency) of the electromagnetic wave that is passing through the material. It shall be understood that when, n, is spoken of it is the value of, n, at the wavelengths where the invention operates. Those are approximately the wavelengths of visible light, 300 nm-1000 nm.
When the conductivity of a material is relevant, it shall be spoken of as the xe2x80x9cconductivityxe2x80x9d. It will not be referred to as a component in the imaginary term of the refractive index. The conductivity is also a function of wavelength. The relevant conductivities are at the wavelengths of light, where the invention operates.
When light is traveling through air and encounters an object with a different index of refraction than air it scatters off of the object. If that object is a sphere the light scatters in a particular way. The scattering of light waves off of a sphere as a function of its radius, index of refraction, and conductivity is a problem that was solved by Gustav Mie in 1908; G. Mie Ann. d. Physik (4), 30 (1908), 377. Mie""s theory is also treated in xe2x80x9cLight Scattering by Small Particles,xe2x80x9d H. C. van de Hulst, Dover, N.Y., 1981, and in xe2x80x9cPrinciples of Optics,xe2x80x9d Max Born and Emil Wolf, Pergamon Press, 4th ed. 1970.
When an electromagnetic wave interacts with another electromagnetic wave a larger or smaller wave can be formed. As shown in FIG. 1 the electric field oscillates up and down from a maximum positive vertical direction, to zero, and down to a maximum negative vertical direction.
When two waves interact and their electric fields are both maximum in the same direction at the same time, the fields add and form a bigger wave. They are said to interfere constructively. They are in phase.
When two waves interact and their electric fields are both maximum but pointing in opposite directions, at the same time the fields add to zero. The waves disappear. They are said to interfere destructively. They are out of phase.
When waves interact and partial constructive and destructive interference along the wave fronts occurs a pattern of maxima and minima is formed. This pattern is called a diffraction pattern. The waves are said to diffract. Diffraction occurs if the difference in phase between the waves is non-random. The phenomena of diffraction relates to this invention.
Polarizing materials are often made of dichroic materials. A dichroic crystal has two refractive indices within along two different axes. The two axes are sometimes referred to as the extinction (absorption) axis and the transmission axis. The refractive index along the extinction axis shall be called nxe2x8axa5. The refractive index along the transmission axis shall be called n11.
The proposed invention uses combinations of polarizing diffusive and reflective materials in conjunction with spherical beads of critical diameter and refractive index defining resonant conditions to achieve an unexpected result.
Various prior art techniques and apparatus have been heretofore been proposed to present three dimensional images on a viewing screen using a stenographic technique such as on a polarization conserving motion picture screen.
See U.S. Pat. No. 4,955,718 to Jachimowicz, et al., U.S. Pat. No. 4,963,959 to Drew, U.S. Pat. No. 4,962,422 to Ohtomo, et al., U.S. Pat. No. 4,959,641 to Bess, et al., U.S. Pat. No. 4,957,351 to Shioji, U.S. Pat. No. 4,954,890 to Park, U.S. Pat. No. 4,945,408 to Medina, U.S. Pat. No. 4,9396,6o58 to Tanaka, et al., U.S. Pat. No. 4,93,755 to Dahl, U.S. Pat. No. 4,922,336 to Morton, U.S. Pat. No. 4,907,860 to Noble, U.S. Pat. No. 4,877,307 to Kalmanash, U.S. Pat. No. 4,872,750 to Morishita, U.S. Pat. No. 4,853,764 to Sutter, U.S. Pat. No. 4,851,901 to Iwasaki, U.S. Pat. No. 4,834,473 to Keyes, et al., U.S. Pat. No. 4,807,024 to McLaurin, et al., U.S. Pat. No. 4,799,763 to Davis, U.S. Pat. No. 4,772,943 to Nakagawa, U.S. Pat. No. 4,736,246 to Nishikawa, U.S. Pat. No. 4,649,425 to Pund, U.S. Pat. No. 4,641,178 to Street, U.S. Pat. No. 4,541,007 to Nagata, U.S. Pat. No. 4,523,226 to Lipton, et al., U.S. Pat. No. 4,376,950 to Brown, et al., U.S. Pat. No. 4,323,226 to Lipton, et al., U.S. Pat. No. 4,376,950 to Brown, et al., U.S. Pat. No. 4,523,226 to Lipton, et al., U.S. Pat. No. 4,376,950 to Brown, et al., U.S. Pat. No. 4,323,920 to Collendar, U.S. Pat. No. 4,295,153 to Gibson, U.S. Pat. No. 4,151,549 to Pautzc, U.S. Pat. No. 3,697,675 to Beard, et al.
These techniques and apparatus involve the display of polarized or color sequential two dimensional images which contain corresponding right eye and left eye perspective views of three dimensional objects. These separate images can also be displayed simultaneously in different polarizations or colors. Suitable eyewear, such as glasses having different polarizing or color separations coatings permit the separate images to be seen by one or the other eye.
U.S. Pat. No. 4,954,890 to Park discloses a representative projector system employing the technique of alternating polarization.
Another technique involves a timed sequence in which images corresponding to right-eye and left-eye perspectives are presented in timed sequence with the use of electronic light valves. U.S. Pat. No. 4,970,486 to Nakagawa, et al., and U.S. Pat. No. 4,877,307 to Kalmanash disclose representative prior art of this type. This time sequence technique also requires the use of eyewear.
There is another example of the timed sequence technique in which the left and right eye views have different polarization""s and are viewed not with glasses but with a single polarized screen over both eyes. The screen is formed of a transparent material that has two or more different polarization coatings. U.S. Pat. No. 5,347,644 to Sedlmayr discloses representative prior art of this type.
Alternating polarization and timed sequence techniques involve photographing the image using two cameras or a dual view camera. The proposed invention involves using a single view conventional camera, but employs a special photographic film. That special film is the proposed invention.
U.S. Pat. No. 5,543,964 to Taylor et al. is another example of superimposing images to create an illusion of depth based on the stereo nature of human vision. Another superimposition technique is shown in U.S. Pat. No. 5,556,184 to Nader-Esfahani.
U.S. Pat. No. 5,559,632 to Lawrence et al. introduces special glasses for viewing regular images in apparent three dimensions employing stereoscopic theory. The proposed invention is not based on stereoscopic theory or superimposition of two dimensional images.
It is known that holographic techniques have been used for three dimensional information recording and display. These techniques involve illuminating a three dimensional object with a coherent monochromatic (laser) beam of light and interfering that light with a reference beam from the same source. The interference pattern is collected on a recording film medium and illumined with the same coherent light from which it was made. The result is a projected image of the object in three dimensions able to viewed without eye wear. Holographic techniques are not in general use because inherent in them are many limitations: an object has its dimension limited to an extent that it can be illuminated by a laser beam; the object should be stationary; a photograph thereof must be taken in a dark room.
Since a laser source has to be used the images obtained are of a single color. This is not useful in most commercial applications. The proposed invention collects an image of a three dimensional scene in apparent three dimensions with incoherent white light. There is no need to illuminate the scene or assembly of objects with coherent monochromatic light. The scene can be moving and recorded as a motion picture. All of the colors in the scene can be recorded.
Some of the limitations of holography have been addressed by a technique known as composite holography.
Composite holography consists of photographing a three dimensional object in a plurality of different directions under usual illumination such as natural light to prepare a plurality of photographic film sections on which two-dimensional pictorial information is recorded. These two dimensional photographs are information images and are separately illumined with coherent (laser) light and are recorded as holograms. These holograms are then simultaneously illumined with coherent (laser) light producing a projection of the perspective information of the three-dimensional object to be recognized by unaided human eyes at different angles depending upon their position with as much effect as one substantially views the image of the three dimensional object.
Composite holography was limited since the size of the recording medium of the holograms had to be large leading to a large sized overall device making it economically impractical. That limitation was resolved by Takeda et al. as disclosed in U.S. Pat. No. 4,037,919. Also in that disclosure is a detailed description of composite holography.
The disadvantage of composite holography is that it involves photographing the object from many different angles and making a hologram of each of those photographic images. This makes it time consuming, laborious and expensive.
The proposed invention overcomes all of the limitations in size, color, and cost of holography and composite holography.
Polarizers, polarizing crystals and photosensitive materials have been combined to produce photographic film by Edwin Land, U.S. Pat. No. 2,997,390. The spherical beads of critical diameter in the proposed invention are absent in Land""s film. Land""s film thus does not collect the three dimensional information in the image, that is collected by the proposed invention.
Polarizing layers and diffusive layers containing diffusive particles have been combined to produce polarizing embodiments for various purposes. Examples of these are found in U.S. Pat. No. 4,268,127, to Oshima, U.S. Pat. No. 5,347,644 to Sedlmayr.
These embodiments lack the spherical beads of critical diameter required to achieve the unexpected result of the proposed invention. They also lack the critical constraints on the refractive index of the proposed invention.
The spherical beads are of dimensions on the order of wavelengths of light. They can be made of glass to high precision. They can also be made of polyethylene. These spheres are grown in chemical reactions by polymer chemists. Duke scientific is a manufacturer of such beads.
There are many types of photographic film that record optical images. In the recording process most of the three dimensional information is lost.
Holography requires a coherent light sources and has limits on the size of the object to be recorded, the number of colors that can be recorded and the cost.
Accordingly several objects and advantages of the proposed invention are:
(a) To produce a photographic film that can record images in apparent three dimensions wherein the film can be used in a standard camera with a single view.
(b) To collect three dimensional information in a photograph where all you do is change the film that you use in the camera.
(c) To collect images in apparent three dimensions with more three dimensional qualities than the present photographic techniques with no substantial increase in cost.
(d) To collect images in apparent three dimensions on a photographic film wherein the physical objects whose images are being collected are illuminated with incoherent white light.
(e) To collect three dimensional optical information on a photographic film of an object wherein the object being photographed without the limitation in size that inhibit holography.
(f) To collect three dimensional optical information of a scene without having to illuminate the scene with a coherent (laser) light source.
(g) To collect three dimensional optical information on a photographic film wherein the image recorded can be viewed in apparent three dimensions without the use of eyewear.
(h) To collect three dimensional optical information of a scene on a photographic film wherein objects in the scene may be in motion.
(i) To collect three dimensional optical information on film, wherein after the film is developed incoherent white light is projected through the film, thus projecting the images onto a viewing screen wherein said images can be viewed in apparent three dimensions without the use of eyewear.
(j) To collect three dimensional images on a film which can then be projected.
(k) To collect three dimensional images on a film that can be a print.